Annulus

Two concentric circles form an annulus of width 10 cm. The radius of the smaller circle is 20 cm. Calculate the content area of the annulus.

Correct answer:

S =  1570.7963 cm²

Step-by-step explanation:

$$\begin{gathered} r_2=20\text{ cm } \\ m=10\text{ cm } \\ {r}_1=r_2+m=20+10=30\text{ cm } \\ {S}_1=\pi \cdot r_1^2=3.1416\cdot 30^2\doteq 2827.4334{\text{cm}}^2 \\ {S}_2=\pi \cdot r_2^2=3.1416\cdot 20^2\doteq 1256.6371{\text{cm}}^2 \\ S=S_1-S_2=2827.4334-1256.6371=1570.7963{\text{cm}}^2 \end{gathered}$$

Try another example

Related math problems and questions:

• Concentric circles
  There is given a Circle K with a radius r = 8 cm. How large must a radius have a smaller concentric circle that divides the circle K into two parts with the same area?
• Circle annulus
  There are 2 concentric circles in the figure. Chord of larger circle 10 cm long is tangent to the smaller circle. What are does annulus have?
• Two annuluses
  The area of the annular circle formed by two circles with a common center is 100 cm². The radius of the outer circle is equal to twice the radius of the inner circle. Determine the outside circle radius in centimeters.
• Annulus
  Calculate the area of two circles annulus k₁ (S, 3 cm) and k₂ (S, 5 cm).
• Concentric circles
  In the circle with diameter, 19 cm is constructed chord 9 cm long. Calculate the radius of a concentric circle that touches this chord.
• Circular lawn
  Around a circular lawn area is 2 m wide sidewalk. The outer edge of the sidewalk is curb whose width is 2 m. Curbstone and the inner side of the sidewalk together form a concentric circles. Calculate the area of the circular lawn and the result round to 1
• Annulus
  The radius of the larger circle is 8cm, the radius of smaller is 5cm. Calculate the contents of the annulus.
• Round skirt
  The cut on the round skirt has the shape of an annulus. Determine how much m² of fabric will be consumed on an 80 cm long skirt. The circumference of the waist is a circle with a smaller radius and is 69 cm.
• Circles
  The areas of the two circles are in the ratio 2:20. The larger circle has a diameter 20. Calculate the radius of the smaller circle.
• Concentric circles and chord
  In a circle with a diameter d = 10 cm, a chord with a length of 6 cm is constructed. What radius have the concentric circle while touch this chord?
• Annulus from triangle
  Calculate the content of the area bounded by a circle circumscribed and a circle inscribed by a triangle with sides a = 25mm, b = 29mm, c = 36mm
• Circular ring
  Square with area 16 centimeters square are inscribed circle k1 and described circle k2. Calculate the area of circular ring, which circles k1, k2 form.
• Circular flowerbed
  Circular flowerbed with diameter 8 m we split by concentric circle to circle and annulus with the same area. Find the radius of the circle.
• Star
  Calculate the content of the shaded part of square with side 28 cm.
• Cutting circles
  From the square 1 m sides, we have to cut the circles with a radius of 10 cm. How many discs will we cut, and how many percent will be wasted?
• 22/7 circle
  Calculate approximately the area of a circle with radius 20 cm. When calculating π, use 22/7.
• Annulus
  Two concentric circles with radii 1 and 9 surround the annular circle. This ring is inscribed with n circles that do not overlap. Determine the highest possible value of n.